// Copyright 2013 Petar Maymounkov
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package ripple

import (
	"sync"
)

// ▒▒
type RefCounter struct {
	zero func()
	sync.Mutex
	numref int
}

func NewRefCounter(zero func()) *RefCounter {
	return &RefCounter{
		zero: zero,
	}
}

func (rc *RefCounter) Reset(zero func()) {
	rc.zero = zero
}

func (rc *RefCounter) Hold() {
	rc.add(1)
}

func (rc *RefCounter) Clunk() {
	rc.add(-1)
}

func (rc *RefCounter) add(change int) {
	var trigger bool
	defer func() {
		if trigger {
			rc.zero()
		}
	}()
	rc.Lock()
	defer rc.Unlock()
	rc.numref += change
	if rc.numref < 0 {
		panic("#")
	}
	if rc.numref > 0 {
		return
	}
	trigger = true
}
